In a quieter time, scant weeks ago, when Roy Dyson was just another determined underdog yipping at the heels of an imposing incumbent, the young state legislator munched fried chicken and served up campaign criticisms at a home-style political dinner in Princess Anne, a small town on Maryland's far Eastern Shore.

The phone rang in the American Legion hall where Dyson was courting votes, and he was called away from the table. He came back, stunned and disbelieving -- and suddenly the favorite in the race.

It was an unlikely position for the low-key legislator, who could still remember begging small-town editors to print his press releases when he ran against the incumbent congressman, Robert Bauman, in 1976.

But this time around, in the final month of the campaign, Bauman would be charged with soliciting sex from a teen-aged boy in Washington and would agree to undergo court-ordered rehabiliation rather than face trial on the charge.And challenger Dyson, the 31-year-old political long shot from southern Maryland, would become the focus of national media attention -- his face on the national network news and his words in all the newspapers.

The unexpected spotlight revealed a politician heavy on warmth and politeness, light on the savvy and caustic wit that had made his opponent a nationally known conservative figure. The voters saw a young state legislator who talked of "sympathy for Bauman's plight," a guy with a "nice smile," as one voter would note, and a candidate so mellow and folksy that he showed off the hole in the sole of the workman's boots he wears to symbolize his "walking campaign" through the district.

But despite polls showing Dyson running as much as 21 points ahead of Bauman, many voters in the final days of the campaign still weren't sure exactly who Roy Dyson was. Said one perplexed citizen, determined not to vote for Bauman: "Sure, I'll probably vote for the other guy. Dy-something. Is that his name?"

If Dyson has failed to make a distinct impression on the voters, it is not for lack of trying. The Democratic legislator has been running for Congress, some said, from the day he entered the Maryland House of Delegates in 1975.

"My impression was that Roy was going to run and going to run and going to run till Bob Bauman either dropped dead or lost," said one state legislator.

The one thing Dyson shares with Bauman is an intense ambition to serve in Congress. He first dreamed of it in 1972 when he left the University of Maryland to take a job as a legislative analyst on Capitol Hill.He saw his chance to get into elective office in 1974 when a new state legislative district was carved out for his native St. Mary's County and its neighbor, Charles. Dyson ran and won, and in 1976 took on the already formidable congressman from Easton, in a campaign other politicians laughed off as a joke. But with little money and even less political support, Dyson surprised a lot of the old pros. He walked away with 46 percent of the vote.

This time around he got more money, about $100,000 in contributions, compared to about $250,000 for Bauman. Still, he was not considered much of a threat until Bauman's Oct. 3 court appearance and the congressman's own admission five days later to the "twin compulsions" of alcoholism and "homosexual tendencies."

These are incidents Dyson refuses to dwell on, but in one private moment on the day that Bauman appeared in court, Dyson found an apt analogy for the way he felt. "It is like going to the funeral of a man you dislike," he said softly. "You don't like what he stood for, but you can't say anything bad about him."

Publicly, Dyson has stuck to that stance, as he did in a recent Baltimore television debate where he asserted: "I believe as election time approaches . . . one's personal integrity and one's personal life is not part of the electoral process."

But privately, Dyson asked plaintively, "What else could I say? On public TV with him sitting next to me. I'm damned if I do, damned if I don't. I'm not used to campaigning on an issue like this."

"I think . . . one's personal life does have a tremendous influence on public life.It has an influence on how you think. The idea of him [Bauman] having another life must have influenced him," Dyson continued until he was suddenly cut off in mid-sentence by his cautious campaign manager, Tony Pappas. "Stick to the program, Roy," Pappas warned him. And that is precisely what Dyson has done.

Last week as Dyson knocked on doors in a Harford County neighborhood of sturdy stone homes that had always been Bauman territory, a middle-aged woman shook his hand and told him, "Both my husband and I were impressed by you [on the debate]. There could have been mudslinging. There wasn't. That's terrific."

Dyson has been hearing that refrain often as he travels on the back roads and down the main streets of the massive district that runs from the Pennsylvania border south along Chesapeake Bay to Virginia. He has put more than 100,000 miles on his old blue van since he started chasing the congressional dream two years ago from his spot in the Maryland General Assembly.

Back in that legislative chamber, Dyson has generally voted the southern Maryland line on issues of strictly local interest to the watermen, tobacco farmers and senior citizens who populate his historic area. But on boarder issues of statewide impact, Dyson, as he himself likes to note, is a maverick. iIt is an image that wins few friends in Annapolis.

In the bitter battle over ratification of the D.C. voting rights amendment, Dyson was the only rural legislator to vote in its favor. It passed the House of Delegates by a single vote.

Rural opponents of the amendment are still screaming. "Roy sold his soul to labor," which was lobbying hard for the amendment. Indeed, labor union political action committees have contributed about $50,000 to Dyson's campaign. Dyson says that he supported voting rights long before he knew labor supported it.

But right now there is just running, the trudging from door to door, the chicken dinners, the Halloween parades, the speeches, the driving in the dark from one end of the district to the other.

There is also the sensation of being the favorite in one of the most closely watched elections in the country. There is the famous NBC anchorwoman traipsing after him as he campaigns, the calls from newspapers as far away as Boston and Houston, and the offer of a TV station's helicopter to fly him around election night.

"I'd be lying," Dyson grinned, "if I said I didn't enjoy it a little."